Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$162.49	13.784%	$184.8876	$184.89	$184.90	$184.90
Purchase #2	$38.43	7.771%	$41.4164	$41.42	$41.40	$41.40
Purchase #3	$224.91	9.874%	$247.1176	$247.12	$247.10	$247.10
Purchase #4	$82.81	9.676%	$90.8227	$90.82	$90.80	$90.80
Purchase #5	$215.92	9.755%	$236.983	$236.98	$237.00	$237.00
Purchase #6	$33.38	13.241%	$37.7998	$37.80	$37.80	$37.80
Purchase #7	$11.68	7.462%	$12.5516	$12.55	$12.55	$12.60
7 purchase totals =	$769.62		$851.5787	$851.58	$851.55	$851.60